I dunno anything about being harder on the rifle but if you read the other thread I linked too, another person completely unrelated to the course measured 20 or so bullets and found 8-12 to have undersized projectiles, some as bad as .221, most about .222 diameter (If I remember right). The ammo is garbage. It's not just my 2 separate crates from 2 different stores, or the other guy on the course. It is very unpredictable what will cause it to happen but it has nothing to do with the rifles. Many guys with MUCH more experience than I have weighed in on this and it is the chinese low quality ammo not the guns.